I think it has been proven, on this site, that an EMP attack isn’t really feasible. To be effecitive it has to be low, and being low makes it’s results limited. A strategic use, over the Pentagon, is another matter.

It hasn’t been disproven at all. In order for an EMP to be effective it has to be very high altitude not low altitude. It’s the cascade effect that make it so powerful. Think of it as an electric avalanche via Compton Scattering.

According to the 2004 Commission to Assess the Threat to the United States of EMP Attack (Executive Report), Several potential adversaries have or can acquire the capability to attack the United States with a high-altitude nuclear weapon-generated electromagnetic pulse (EMP). A determined adversary can achieve an EMP attack capability without having a high level of sophistication.

It goes on to briefly address the effects, EMP is one of a small number of threats that can hold our society at risk of catastrophic consequences. EMP will cover the wide geographic region within line of sight to the nuclear weapon. It has the capability to produce significant damage to critical infrastructures and thus to the very fabric of US society  The Commissions chairman has testified that within one year of such an attack, 70%  90% of Americans would be dead from such causes as disease and violence. It is also highly plausible that many Americans would die of starvation due to the interruption of the national food supply.

According to the Washington Department of Health, Office of Radiation Protection, A 1.4 Megaton bomb launched about 250 miles above Kansas would destroy most of the electronics that were not protected in the entire Continental United States.